1. Field of the Invention
The invention relates to a linked conveyor that is also commonly called a sorter for the sorting of small cargo units, such as packages in post offices.
2. Description of the Related Art
Such sorters are known in different configurations. The basic principle is that small cargo units that occur in unsorted sequence, for example, with pieces of luggage in airports that must be transported, eventually only after an extended waiting period, to specific terminal gates, are sorted according to certain criteria by putting small cargo pieces on the sorter that have been coded for this purpose before they have been loaded on the sorter at least one loading station (if necessary by hand; generally, however, by means of a suitable loading device) and that are then transported by the sorter to a predetermined delivery station where they are suitably unloaded from the sorter from the side.
For this purpose the small cargo units that are to be sorted are individually placed on a transport position of the sorter before or while being placed on the sorter (if there are multiple loading stations), which is preferably on the next free conveyor position that approaches a loading station of the sorter in order to make the most efficient use of its conveying capacity.
Several possibilities/configurations are known that allow a defined delivery at the predetermined delivery station. For example, so-called "pushers" are known that are located to the side of the conveyor opposite a delivery station which push the small cargo unit off the sorter and which are activated perpendicular to the moving direction of the sorter. This type of unloading of small cargo units, however, is completely unsuitable for several types of cargo and higher conveying speeds because relatively high pusher activation speeds are needed due to the relatively short unloading time that will be available to the small cargo unit with a pushing power of proportionate force when the pusher pushes the small cargo unit.
Another known possibility of unloading of small cargo units consists in pivoting a stationary deflector arm at the delivery station. However, this unloading or delivery method can be seen to work well only for sorters with a relatively slow conveying speed, and even then will have the disadvantage that a small cargo unit that is to be unloaded will be turned about its vertical axis relative to its conveying speed, and even then will have the disadvantage that a small cargo unit that is to be unloaded will be turned about its vertical axis relative to its conveying direction if it hits an inwardly pivoting deflector so that, particularly with relatively long small cargo units, an uncontrolled relative movement may occur between the small unit, on the one hand, and the sorter and respective delivery station on the other.
For the aforementioned types of sorters it is obviously not necessary to configure the sorter as a linked conveyor, although this is generally useful for the aforementioned modes of delivery operation, as well.
In addition, so-called tilting-shell sorters are known that are configured as linked conveyors where the top-end segment of each conveying element carrying the carrier body or carrier plate can be pivoted from its generally more or less vertical transport position into a tilted unloading position at the delivery station causing the small cargo unit it contains to slide off laterally at the predetermined delivery station. Different configurations are known for such tilting-shell sorters. Their underlying principle is that at each delivery station a stationary shell body device is located that can possibly engage an approaching cam device in such a manner that the shell body is pivoted in the aforementioned manner and returned (and locked) to its upright transport position after passing the delivery station of the conveying element.
Even with this type of tilting-shell sorter a rolling over (tumbling) of the unloaded small cargo unit can occur, although meanwhile several configurations have become known that permit a rather more defined and gentle delivery. This is, for example, the case whenever the shell body is simultaneously lowered during the unloading process. Still, even with these types of shell body conveyors it can generally not be avoided that the small cargo units to be unloaded are dumped onto a lower level, which can be disadvantageous for fragile cargo.
In order to be able to unload particularly fragile small cargo units from a sorter precisely at the predetermined delivery station, without having to overcome frictional resistance that frequently causes the small cargo unit to twist during the unloading procedure and without the risk of rolling over, precisely and on target as well as at essentially the same level and thus, in general, extremely gently land accurately, sorters have been developed whose loading and unloading positions consist of so-called crossbelt conveyors.
These cross-belt conveyors feature endless conveyor belts that run over two rollers or cylinders that are positioned apart from each other and that extend in the direction of the conveying movement of the sorter. One of these rollers is to be driven (possibly via a transmission) by an electric motor that is located at the conveying element in question (or at an adjacent element) and thus rotates synchronously with the sorter in such a way that the carrying cross-belt conveyor of a conveying element is supported by a fixture that is connected by a element, thereby forming a linked chain made up of all the support fixtures. The fixture is supported and guided at its lower end segment that faces away from the cross-belt conveyor by two (support and guide) rails that are positioned apart from and parallel to each other and that determine the predetermined conveying distance.
When a conveying element on this type of conventional sorter carrying a small cargo unit approaches the predetermined delivery station, the drive of the cross-belt conveyor receives a start signal, once the small cargo unit reaches the delivery station, and is connected to a power source so that the small cargo unit in question can be carried off, laterally and perpendicular to the conveying direction of the sorter, by the cross-belt conveyor toward the delivery station at undiminished speed that, today, is relatively high. The small cargo unit is received (possibly via a slide) by a receiving device (that may be a container or another conveyor) whose receiving surface is, if possible preferably at the same level as the upper surface of the carrying segment of the cross-belt conveyor.
The electric motors of the cross-belt conveyor receive their electric (drive) power via electrical lines that are connected to a stationary power rail through sliding contacts of the conveyor element in question. The power rail is connected to an electrical power source, as is known, for example, in relation to streetcars or underground trains and that is regularly used whenever a mobile unit that features an electrical drive must be supplied with electrical energy from a stationary power source.
It is a significant disadvantage of this known sorter that its sliding contact system is subject to considerable wear since the sliding contacts move relative to the power rail and are permanently pressed hard against it, which inevitably causes a significant amount of friction and heat to develop. The known conventional sorter is, therefore, very expensive not only in regard to installation costs but also in regard to the required maintenance and repair. In addition, any maintenance and repair will render the sorter, and thus the entire conveying system, inoperative, a circumstance that is already rather problematic in sorting installations of the postal organization or mailorder businesses and that is entirely unacceptable for luggage distribution and their respective sorting installations in airports.
In order to avoid these and other disadvantages, it has already been suggested to equip conventional sorters with friction wheels that are set into rotary motion by the rails when the sorter is operated and that interface with generators that produce the electrical power required for the operation of the cross-belt conveyors. While in this type of sorter the significant wear between the sliding power contacts and the power rail (and the pollution caused by it) has been eliminated, it has been found that significant wear occurs between the friction wheels and the support and guide rails, on the one hand, and between the friction wheels and the generators, on the other, due to the inevitable slippage causing not only also significant pollution but also, as a consequence, frequent maintenance and repair work. This is the case, if for no other reason, because the wear from friction continuously causes the frictional contact between the friction wheels and the rails and the respective generators to be reduced, causing the power generated by the generators to vary from conveying element to conveying element, an, in certain cases, may be too low to supply the power required to actuate a drive for a cross-belt conveyor.